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There are a few reports that I need my employees to have access to, but there are many reports I do not want them to have access to. The problem with the software is, it is all or nothing for reports. I can not set it up so they can see the ones that need, without giving them access to ones they should not be seeing. Printing price tags is the biggest headache for me.

It is way too long to try to explain, just know if you want to print price tags before you finalize an order this is not the program for you! If there system is down, you are dead in the water. Since April 17th till today July 17th I have experienced 6 outages that ranged from 5 minutes to an hour. Yes that is when customers walk out the door.

I am paying for this service and they are costing me money. No spot for check numbers. Anytime the cash drawer is opened a receipt is printed, and every time a receipt is printed the cash drawer open There is no auto fill for customer names or items. There is no warning of duplicate UPC's or Customer names. There is no customer loyalty program or rewards program in the system, I have to pay an outside company in order to give my customers a rewards program. I used quickbooks point of sale before, and I changed because I needed a web based program. If you were to do this do not go with a long term contract.

I don't think you can really use the trial period effectively, to see all the ins and outs of the system. I will be switching to a new POS system as soon as my contract is up. I tried unsuccessfully to terminate the contract early. If anyone is seriously thinking of using Lightspeed, I highly recommend that you sit down and make a list of exactly what you want, how they can help your business succeed on the smallest detailed level, not a generalized list things they say they will do by signing with them. Ask a lot of questions. And assume absolutely nothing. Just assuming that I would have a functioning backend database was my downfall.

The frontline customer service agents who answer the phones. Anyone past that frontline defense is a joke. Honestly, there isn't enough time in my day to go through the four years of hassle and issues they caused for my business. I know for a fact that Lightspeed is the entire reason why I ended up closing my storefront business. There were so many problems and issues that they were aware of, but because it was only happening to a small few, they wouldn't work on fixing the problems, but were very happy to give me a 'work-around' that usually ended up not working either.

You also can tell the company by the ability to talk to management With Lightspeed, they won't let you call and talk to a supervisor. Agents are not allowed to transfer an existing customer to a supervisor or manager, only allows the management to call you. There are no emails available, list of names for various departments, and definitely no phone extensions to get further help. They do not stand by their product, therefore, there is no reason to stand by them. Ease of use given how flexible and intricate the program is. Browser based for legacy PCs - with multiple browser tabs allowed to easily switch between POS modules.

Even works on smartphones for quick updates and status checks. Cloud based - therefore, access your business information anywhere you are Internet connected. Great support staff - knowledgeable, friendly and insightful. Item sold on-line via eCom is immediately updated to the cloud and reflected in POS and vice versa. While the POS and eCom integration is wonderful, you still must manage inventory on both platforms in order to get the desired results. For example, when new inventory arrives you receive the items through your POS based purchase order.

However, you then need to access eCom to update public facing product narratives, SEO related fields, related products, additional category related references, etc.. So, while both programs are great and work together - it will be even better when FULL integration of the two programs is achieved. Quick reliable and organized access to: A software system that allows me to create POs, send them electronically to vendors, document all aspects of product ordering. A system that provides an eCommerce public facing front-end that is highly customizable.

Front end looks pretty. Sales team is helpful in getting you signed up. Lots of deals to entice you to sign up for that year long package. It does actually link your inventory when everything is working properly. Sure they have live chat, a call system that will call you back so you don't have to wait on hold, and email help.

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But the majority of the time no one can actually help you solve your issue. A lot of "we're looking into that" and "I'll let our tech team know" or "browser was your customer using when they were unable to checkout? Not one, not twice, but 3x cart oversold in the first 7 months of using this POS with web store. They can't tell you why, or fix it, or offer any help.

They will ask you what browser your customers were using though. Orders not downloading from web store so you are actually aware that there is an order waiting to be shipped, as well as the inventory not updating. Very small maximum of characters in product descriptions that can display on web store. Hopefully your product photos speak for themselves because no room for in depth explanations, videos, etc.

Generally about 3 days. I can't discount a single product in the app, and discount applies to every product in the sale. Not annoying at all. Limited customization of web store. If you are looking for an all-inclusive solution to your brick and mortar POS and online store needs, please look elsewhere. I came from Square which is much simpler to navigate, more appealing on the backend, and does not even charge a monthly fee.

There are tons of options out there for POS solutions, standalone or including online, I suggest you find a better one. Our experience with several POS systems over the years indicates that it is important to understand how a proposed POS system works and what the costs are and what the assurance is that the system will work for us. Time spent in learning how well the POS matches our processes is very important.

Fortunately, we took the time to go over our needs in depth with Lightspeed sales and were able to be sure the solution fit our needs before purchase. We are very happy with our Lightspeed product and service. We have used Lightspeed Retail for about 5 years and have integrated it with their Webstore ecommerch for 2 years before changing over to Lightspeed Ecom for the past 8 months.

Getting POS and integrated ecommerce to work together takes more work than most people realize, so it is important to have technical support available that is willing and competent. We have found Lightspeed to be flexible enough to work with our preferences for POS and ecommerce. And, we have had excellent experience particularly with the Ecom help and also with Lightspeed POS help. We have found very few problems with the POS and Ecom products. There is a small rounding issue so that occasionally PO's need to be adjusted by a few cents to match an invoice amount from a supplier.

We have almost always been able to get the results we need by calling tech support and telling them what we are wanting to do and getting their suggestions about possible solutions. Lightspeed's customer support is excellent overall. At least half the time when we experience a problem, it's due to our lack of understanding rather than a shortfall of the product. Their responses are usually prompt and helpful. Also, in almost three years of using the product, we have had virtually zero downtime and have seen nary a hiccup through numerous system updates and the occasional hotfix. Tons of valuable information for every product we sell.

And in contrast to some other systems that try to pack everything on a single page, Lightspeed Retail allocates product information across a menu of pages so you can quickly navigate to the data you want and ignore what you don't want. And much of the information is searchable in ways that help our business create purchase orders and determine which products to stock or discontinue.

We have been cautious in taking advantage of partnerships available through Lightspeed i. Some aspects of ongoing database management are not transparent to the technically nonproficient user. Our efforts to clean up the clutter of stale information are not always successful. And some types of searches are not well supported so far. It's not the people, really. Anyone you speak to are fabulous, however, the company ties their hands in what they can do.

They have so many qualified and skilled people, but the company has focused on growing worldwide and not actually the logistics of knowing what their own policies and procedures are. Customer Support is constantly trying to put out fires and fix issues in Production instead of figuring all that out in the Testing Phase. And if you actually find a problem in which the Support staff agrees is a problem and creates a ticket for it, when it goes to the next lead programmer, they tend to dismiss it and never let you know. The Customer Support Staff that you talk to from, unfortunately, the only one phone number they have available.

All emails are the same but are coded in a way that they will go back to them but only if they send you an email directly. If you expect someone in management to contact you but they don't, you're screwed. And since there is only one phone number to use to call, that only gives you the general support staff or Billing. What I have generally found is that Support understands exactly what's going on and understands what you are going through and what needs to be done. It's the second line of defense that who think you're crazy, or the standard comment is that they are aware of the problem and are working on it.

However, the problem isn't listed anywhere in the CMS that the customers are allowed to see If you think this company will have your back, you will be extremely disappointed!!!

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They seem to only care about growing the number of offices they have internationally and not making sure these offices are completely integrated and the staff that are supposed to be helping you are actually allowed to access the tools, I believe, they are more than qualified to do. Run far far away!!! They will mislead you to get you into the contract. They do not care about the business or business owner. Their customer service is Horrible. They would rather argue with you than help you and never call back when they say they will. I have been with them for 3 years and would love to get out but they have me locked in for another year and they won't budge.

Log in as an employee and click export in the items screen or the customer screen. In two clicks they have your entire business. Managers can not build, send or check in purchase orders without seeing all costs and profits.

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They don't care and will just keep coming out with new items to charge for that should just be ongoing upgrades to their core system such as the new analytics. They have come out with over 4 new items to charge for while not fixing the issue they knew about for over two years. They just don't care.

Good looking, can be used easily. The software itself isnt horrible it is the service and the fact that they dont care about you or your business and they will not fix major issues within the software. Customer service is horrible, your employees can down load all items with costs, profit, margin, and your entire customer base and there is no fix and they don't care.

Lightspeed's products have one strong point: A broad set of features. Lightspeed has made sure to buy software with a lot of capabilities to resell. Unfortunately, this means that they don't seem to actually know how their software works. In the three years I've been using their software it's been the most unreliable and unstable piece of software I've ever used. Their desktop program still crashes on a daily basis and many functionality problems have not been fixed. The current version of our website has been running for about a year with major functionality problems that, to my knowledge, Lightspeed hasn't even looked into.

The new version eCommerce which we're being forced to upgrade to, isn't actually finished or feature complete. They claim to support payment processors that they don't support, and of the few that are supported some of them aren't even functional in Canada, the country where Lightspeed is located. They clearly don't take customer service or their clients' business seriously. With the amount of problems we've had and the amount of money we've spent, I would expect some sort of account manager to contact us and make sure everything is working smoothly in order to retain us as a customer, but that just doesn't seem to be a priority.

Make sure to explore all your options before making a decision if you're considering Lightspeed as your POS system. We've been using Lightspeed Retail for close to a year now and have been very happy. My biggest compliment is how user friendly the entire platform is. The system is very intuitive which saves me hours when training a new employee. Any computer-literate person can jump in and figure out the essentials on their own in a matter of minutes. I've had to call customer support several times over the last year, and each time has been a pleasant experience.

Most recently, I was on hold, waiting for a representative to pick up. After about 30 seconds, I was offered to have them call me back once one became available. It worked well because I could go back to working on other things. About 20 minutes later, I got the call, the rep immediately fixed one of my issues, then said he'd have our account manager call back to help with my other question he wasn't able to make the changes I was requesting.

Our account manager called back later that day, and after doing some research, got us exactly what we were hoping for. I can understand people's dissatisfaction with being on hold or waiting for someone to call you back. If it's an urgent issue, that would be very frustrating. Maybe we've been lucky, but none of the issues I've had to call about have been time sensitive so it worked really well having them call me back instead of being stuck on the phone waiting for someone to pick up.

All in all, we've be very satisfied with their service. Hopefully things continue to improve! Honestly, I have very little complaints. Maybe have more support reps so there's no hold time? But I realize adding the extra staff would get expensive quick. Give it a try! I believe they offer month to month subscriptions so there's very little investment. We made the switch to Lightspeed, from Quickbooks, in during a major expansion of our sq ft retail clothing store. It was the perfect choice to meet our quickly growing needs for a better organized and more functional way to track inventory, make sales and view reports -- in fact, we really regretted not switching earlier!

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The easy to use POS screen made training our employees a breeze and ensures that sales data is captured completely and systematically for each transaction -- something we didn't have the ability to do when we were hand-typing each sales invoice in Quickbooks. Plus, the addition of integrated hardware a barcode scanner, barcode label printer, cash drawer and receipt printer accomplished even more than faster transaction time and more accurate inventory records -- it made our sales staff seem more professional and our customers feel more comfortable.

Inventory tracking is one of the biggest strengths of this software. You can determine how much information you want to enter about each product, depending on what data you want to collect - multiple suppliers and costs, UPC codes, margins, related products and packaging It was revolutionary for us to be able to know exactly what we have in inventory instead of confusing spreadsheets full of inconsistently described merchandise.

We love that we can see detailed information about which products we have on the floor versus what's in storage, that we can quickly compare expenses with profits, and that we can create reorders and customer - specific orders with a couple of clicks. We also added the Lightspeed webstore when we switched to Lightspeed - and we're so happy that we did. We'd tried using several different platforms for an online shop, but kept running into the nagging issue of inventory maintenance since we were listing the same products online that were for sale in our brick-and-mortar shop.

Lightspeed provides us with an integrated inventory for both stores, updating our database live, so that we never sell the same item twice. Products are easy to add to or remove from the webstore and web sales are easy to track. Plus we were able to do quite a bit of customization ourselves, adding both functionality and attractiveness to the existing template. We'd recommend that if you're going to use the Lightspeed web store, you work closely with a web developer who can help you get the most out of this great feature.

Lightspeed customer service has been impeccable. They're fast, kind and very knowledgeable. Plus they really seem to care that you and your business succeed, with the help of their software. We'd recommend that you purchase the Maintenance Plan so that you get instant access to their support gurus. It's an easy interface to navigate. Sometimes, the support is friendly. Sometimes, the support is useful. It's ok if you're a small boutique, but if you have thousands of SKUs take a pass - Lightspeed can't handle it.

It's constantly stalling and and crashing. Support told us we needed new computers. We did that - no improvement and we're out thousands in unnecessary computer upgrades. The support team straight up lies to tell you a feature is coming until you re-sign, then tell you that feature was never being worked on and won't be anytime soon.

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There are simple things like splitting a receipt into multiple gift receipts a must for a major retail store selling multiple gifts to one person that Lightspeed can't do. You have to ring each transaction in separately, upping your checkout time hugely. Every restaurant software on the market can split bills, but for some reason, LS can't.

Support is fair at times, surly at others. You can just tell everyone working on it has zero understanding of what a functioning retail store is actually like. If you run a sales report for seasonal products you sold last summer for example, it will include every product you've ever had, whether it's current or not. I could go on for ever. Their customer support generally tries to be helpful and you can almost always reach someone.

They maintain a suggestion board and try to address common issues there. Doesn't do "negative on hand" but instead auto-adds to inventory sometimes auto-receiving from PO's which can make actual inventory tracking a complicated nightmare. Non-intuitive search which is not inclusive of all fields. Inability to track total changes before finalizing inventory counts. Some serious randomness in auto-combining items during initial import. Complete inability to search custom fields.

As a bookstore, we need to be able to search by author - but author is a custom field, so completely unsearchable. We ended up having to make put all our author names in the "brand" field to make them searchable. It's almost useless if the author has numerous co-authors. I am truly afraid to see what kind of inventory count discrepancies we'll have at the end of the year based on the way the year started with the most random and enormous cluster of import issues. The software, as a whole has some odd programming choices that I never would have thought to ask about before signing on -- because they're completely foreign to every other POS system I've used, like who would think to ask if they allow negative numbers?

They're cloud-based, which is great for accessing remotely but also allows them to be constantly updating which can cause issues. I wish that they would update at specific intervals and provide customers with update logs. I moved from Checkout for Mac to LightSpeed when my needs required more accurate reporting and a more thorough online presence.

I had absolutely no problems with the transfer of data over and the ease in setting up new products is seamless, once the concept is explained. Their technical support team is wonderful and has always resolved any of my issues right away. I love the ease in use of the checkout. I have several seasonal employees and assuming they remember their passwords, can jump right back in where they left off, no retraining needed.

My husband loves the incredible detail of the reports and the import into Quickbooks works just fine. I set this up on my own also That way you already have questions in mind and they can review what you have established. We have over sku's, LightSpeed handles it seamlessly. In the event of an minor outage, the IT team jumps to fix the issue promptly. I also added Cayan payment processing and their Genius terminal. No more double entry and payments are accurately reported. I love that this terminal communicates with the program without the use and expense of a payment bridge. They also reduce my monthly processing charges.

I haven't once regretted coming onboard. Accurate reporting and a more thorough online presence. Ease of transfer of data over and in setting up new products Quick to respond technical support team ADDED - Cayan integrated payment processing and their Genius terminal. If internet is down, you can't do anything. No automatic notice of duplicate customer names.

No automatic account creation of customer names with credit card payments. Unable to add single item on multiple item sale to special order.

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Lightspeed suffers from frequent changes in the product. For our store, with over items and integration with a web store, it is a very big investment in time and money to change systems. Since we've been on lightspeed, they have developed and cancelled three different e-commerce products: All of these have now been cancelled and we are left with a month to scramble to come up with a replacement. They are trying to coerce us to switch to their latest platform.

No thanks, we've learned our lesson. Lightspeed treats their products as short-term relationships that can be simply discarded for the next new shiny thing. The real business software would provide an upgrade path and help customers through it. Find a company that can provide a stable platform. Lightspeed can not, it's not in their DNA. Decent features, though e-commerce is really weak, as is inventory management you have to export to excel, do counts, and re-import.

None of our staff can figure this out--it is complex and error prone. Horrible continuity of product. Multiple software products are thrown away with customers left hanging with no transition plan. We deeply regret placing our trust in Lightspeed. It does not appear that the designers have ever actually worked in the retail business. My biggest complaint is the lack of control in tracking inventory and the two biggest problems are: The options to do so are either to manually adjust the quantity on hand, which means you have no visibility as to why stock has disappeared, or to can "sell" it to yourself, which gives you visibility as to movement, but now you have to adjust your sales reports to remove the fake sales.

This is a problem for two reasons: The wrong SKU stills says zero on hand, but the correct one says you still have it in stock when it isn't. The second problem occurs if an item gets sold before it was received. LS automatically adds an item to complete the sale bringing the quantity on hand to zero, but then, when it gets received, the quantity on hand shows one.


The correct solution is for the quantity to go negative, then when the item is received, it zeros out, or you can run a report of negative items so you find the ones that have been sold incorrectly. Other issues I have is the lack of customizing for reports, they are all canned so I end up running multiple different reports to get the same information I used to get with one report in my old system.

The system does not allow for part numbers instead using the product description to identify items. This makes searching for items more tedious, LS's presumption is that you will always have a scanner and a scannable tag on the item but just isn't the case in real life. Really take the time to do a thorough demo of any product you are looking at.

Take the time to think of all the usual and unusual transactions you do on a daily, monthly, and annual basis, and require the vendor to show you how their system supports that. Easy to use IF you can get past all the problems which are nearly daily. There really are not enough pros to make it worth listing. Get away from this POS and find a different one!

I've called dozens of times to get the star receipt printer fixed and usually it's an every week thing. I had the ecom too but was not able to use it at all. You have to put every item in one at a time. I don't have time for that. They don't offer much help there. Everytime they do an update I lose data that I have added. Because this system is so dysfunctional I have also lost customers in my store. I managed to get a partial refund for ecom. Salespeople are as bad as scammers. They said it will hook up with quick Books but it won't. You put money on this program and you will wish you didn't.

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The upper management even lies. I have had so many service calls to fix things I have lost count. This company should be shut down. I'm a small business that opened May I have no idea what my inventory count is because this system can't even do that. With the amount of money, this cost me I'm tempted to take them to court. These people are guilty of false advertisement. Find your software someplace else and don't get scammed by these liars.

Benefits were stress, headaches, lost customers, lost money, ripped off, as screwed by liars. We run a one location bicycle sales and repair shop in NJ. For the past 10 years we used Microsoft Dynamics Point of Sale. Because Microsoft chose to exit the Point of Sale space, we needed to replace our system, with something that was flexible, cloud based, and expandable.

In modern quantum physics , the electromagnetic field is described by the theory of quantum electrodynamics QED. In this theory, light is described by the fundamental excitations or quanta of the electromagnetic field, called photons. In QED, photons are massless particles and thus, according to special relativity, they travel at the speed of light in vacuum. Extensions of QED in which the photon has a mass have been considered. The limit obtained depends on the model used: Another reason for the speed of light to vary with its frequency would be the failure of special relativity to apply to arbitrarily small scales, as predicted by some proposed theories of quantum gravity.

In a medium, light usually does not propagate at a speed equal to c ; further, different types of light wave will travel at different speeds. An actual physical signal with a finite extent a pulse of light travels at a different speed. The phase velocity is important in determining how a light wave travels through a material or from one material to another. It is often represented in terms of a refractive index. The refractive index of a material may depend on the light's frequency, intensity, polarization , or direction of propagation; in many cases, though, it can be treated as a material-dependent constant.

The refractive index of air is approximately 1. In exotic materials like Bose—Einstein condensates near absolute zero, the effective speed of light may be only a few metres per second. However, this represents absorption and re-radiation delay between atoms, as do all slower-than- c speeds in material substances. As an extreme example of light "slowing" in matter, two independent teams of physicists claimed to bring light to a "complete standstill" by passing it through a Bose—Einstein condensate of the element rubidium , one team at Harvard University and the Rowland Institute for Science in Cambridge, Mass.

However, the popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrarily later time, as stimulated by a second laser pulse. During the time it had "stopped," it had ceased to be light. This type of behaviour is generally microscopically true of all transparent media which "slow" the speed of light. In transparent materials, the refractive index generally is greater than 1, meaning that the phase velocity is less than c.

In other materials, it is possible for the refractive index to become smaller than 1 for some frequencies; in some exotic materials it is even possible for the index of refraction to become negative. A pulse with different group and phase velocities which occurs if the phase velocity is not the same for all the frequencies of the pulse smears out over time, a process known as dispersion.

Certain materials have an exceptionally low or even zero group velocity for light waves, a phenomenon called slow light , which has been confirmed in various experiments. None of these options, however, allow information to be transmitted faster than c. It is impossible to transmit information with a light pulse any faster than the speed of the earliest part of the pulse the front velocity.

It can be shown that this is under certain assumptions always equal to c. It is possible for a particle to travel through a medium faster than the phase velocity of light in that medium but still slower than c. When a charged particle does that in a dielectric material, the electromagnetic equivalent of a shock wave , known as Cherenkov radiation , is emitted. The speed of light is of relevance to communications: This applies from small to astronomical scales. On the other hand, some techniques depend on the finite speed of light, for example in distance measurements.

In supercomputers , the speed of light imposes a limit on how quickly data can be sent between processors. Processors must therefore be placed close to each other to minimize communication latencies; this can cause difficulty with cooling. If clock frequencies continue to increase, the speed of light will eventually become a limiting factor for the internal design of single chips.

Similarly, communications between the Earth and spacecraft are not instantaneous. There is a brief delay from the source to the receiver, which becomes more noticeable as distances increase. This delay was significant for communications between ground control and Apollo 8 when it became the first manned spacecraft to orbit the Moon: As a consequence of this, if a robot on the surface of Mars were to encounter a problem, its human controllers would not be aware of it until at least five minutes later, and possibly up to twenty minutes later; it would then take a further five to twenty minutes for instructions to travel from Earth to Mars.

NASA must wait several hours for information from a probe orbiting Jupiter, and if it needs to correct a navigation error, the fix will not arrive at the spacecraft for an equal amount of time, creating a risk of the correction not arriving in time. Receiving light and other signals from distant astronomical sources can even take much longer. Astronomical distances are sometimes expressed in light-years , especially in popular science publications and media. Proxima Centauri , the closest star to Earth after the Sun, is around 4. Radar systems measure the distance to a target by the time it takes a radio-wave pulse to return to the radar antenna after being reflected by the target: A Global Positioning System GPS receiver measures its distance to GPS satellites based on how long it takes for a radio signal to arrive from each satellite, and from these distances calculates the receiver's position.

The Lunar Laser Ranging Experiment , radar astronomy and the Deep Space Network determine distances to the Moon, [83] planets [84] and spacecraft, [85] respectively, by measuring round-trip transit times. The speed of light has become important in high-frequency trading , where traders seek to gain minute advantages by delivering their trades to exchanges fractions of a second ahead of other traders.

There are different ways to determine the value of c. One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam, with their product equalling c. Consequently, accurate measurements of the speed of light yield an accurate realization of the metre rather than an accurate value of c.

Outer space is a convenient setting for measuring the speed of light because of its large scale and nearly perfect vacuum. Typically, one measures the time needed for light to traverse some reference distance in the solar system , such as the radius of the Earth's orbit. Historically, such measurements could be made fairly accurately, compared to how accurately the length of the reference distance is known in Earth-based units.

It is customary to express the results in astronomical units AU per day. The distance travelled by light from the planet or its moon to Earth is shorter when the Earth is at the point in its orbit that is closest to its planet than when the Earth is at the farthest point in its orbit, the difference in distance being the diameter of the Earth's orbit around the Sun.

The observed change in the moon's orbital period is caused by the difference in the time it takes light to traverse the shorter or longer distance. Another method is to use the aberration of light , discovered and explained by James Bradley in the 18th century. A moving observer thus sees the light coming from a slightly different direction and consequently sees the source at a position shifted from its original position. Since the direction of the Earth's velocity changes continuously as the Earth orbits the Sun, this effect causes the apparent position of stars to move around.

From the angular difference in the position of stars maximally An astronomical unit AU is approximately the average distance between the Earth and Sun. By combining many such measurements, a best fit value for the light time per unit distance could be obtained. The relative uncertainty in these measurements is 0.

A method of measuring the speed of light is to measure the time needed for light to travel to a mirror at a known distance and back. On the way from the source to the mirror, the beam passes through a rotating cogwheel. At a certain rate of rotation, the beam passes through one gap on the way out and another on the way back, but at slightly higher or lower rates, the beam strikes a tooth and does not pass through the wheel.

Knowing the distance between the wheel and the mirror, the number of teeth on the wheel, and the rate of rotation, the speed of light can be calculated. The method of Foucault replaces the cogwheel by a rotating mirror.

Interstellar Travel: Approaching Light Speed

Because the mirror keeps rotating while the light travels to the distant mirror and back, the light is reflected from the rotating mirror at a different angle on its way out than it is on its way back. From this difference in angle, the known speed of rotation and the distance to the distant mirror the speed of light may be calculated. Nowadays, using oscilloscopes with time resolutions of less than one nanosecond, the speed of light can be directly measured by timing the delay of a light pulse from a laser or an LED reflected from a mirror. One option is to measure the resonance frequency of a cavity resonator.

If the dimensions of the resonance cavity are also known, these can be used to determine the wavelength of the wave. In , Louis Essen and A. Gordon-Smith established the frequency for a variety of normal modes of microwaves of a microwave cavity of precisely known dimensions. A household demonstration of this technique is possible, using a microwave oven and food such as marshmallows or margarine: Interferometry is another method to find the wavelength of electromagnetic radiation for determining the speed of light. Before the advent of laser technology, coherent radio sources were used for interferometry measurements of the speed of light.

The precision can be improved by using light with a shorter wavelength, but then it becomes difficult to directly measure the frequency of the light. One way around this problem is to start with a low frequency signal of which the frequency can be precisely measured, and from this signal progressively synthesize higher frequency signals whose frequency can then be linked to the original signal. A laser can then be locked to the frequency, and its wavelength can be determined using interferometry. Until the early modern period , it was not known whether light travelled instantaneously or at a very fast finite speed.

The first extant recorded examination of this subject was in ancient Greece. Einstein's Theory of Special Relativity concluded that the speed of light is constant regardless of one's frame of reference. Since then, scientists have provided increasingly accurate measurements. Aristotle argued, to the contrary, that "light is due to the presence of something, but it is not a movement". Based on that theory, Heron of Alexandria argued that the speed of light must be infinite because distant objects such as stars appear immediately upon opening the eyes.

Early Islamic philosophers initially agreed with the Aristotelian view that light had no speed of travel. In , Alhazen Ibn al-Haytham published the Book of Optics , in which he presented a series of arguments dismissing the emission theory of vision in favour of the now accepted intromission theory, in which light moves from an object into the eye. In the 13th century, Roger Bacon argued that the speed of light in air was not infinite, using philosophical arguments backed by the writing of Alhazen and Aristotle. In the early 17th century, Johannes Kepler believed that the speed of light was infinite, since empty space presents no obstacle to it.

Since such misalignment had not been observed, Descartes concluded the speed of light was infinite. Descartes speculated that if the speed of light were found to be finite, his whole system of philosophy might be demolished. Fermat also argued in support of a finite speed of light. In , Isaac Beeckman proposed an experiment in which a person observes the flash of a cannon reflecting off a mirror about one mile 1.

In , Galileo Galilei proposed an experiment, with an apparent claim to having performed it some years earlier, to measure the speed of light by observing the delay between uncovering a lantern and its perception some distance away. He was unable to distinguish whether light travel was instantaneous or not, but concluded that if it were not, it must nevertheless be extraordinarily rapid.

The actual delay in this experiment would have been about 11 microseconds. In , James Bradley discovered stellar aberration. The following year Gustav Kirchhoff calculated that an electric signal in a resistanceless wire travels along the wire at this speed. It was thought at the time that empty space was filled with a background medium called the luminiferous aether in which the electromagnetic field existed.

Some physicists thought that this aether acted as a preferred frame of reference for the propagation of light and therefore it should be possible to measure the motion of the Earth with respect to this medium, by measuring the isotropy of the speed of light. Beginning in the s several experiments were performed to try to detect this motion, the most famous of which is the experiment performed by Albert A. Michelson and Edward W. Modern experiments indicate that the two-way speed of light is isotropic the same in every direction to within 6 nanometres per second. Dax Dasilva founded Lightspeed in to help businesses re-create an online shopping experience that offered convenience, personalization and product information.

In August of that same year, the company was named winner of the 5th Annual Innovative Award - Software Applications for their product, Lightspeed for iPad, which was designed to offer the ease-of-access, value and speed typical of the online shopping experience to brick-and-mortar retail businesses. Considered the first interactive POS platform of its kind, Lightspeed for iPad armed retailers with powerful sales and inventory management tools and helped to speed up the customer checkout process. The 3, square foot space, which houses its US sales team and demonstration showroom would come to serve as a training center for retailers.

Known for hosting numerous retail innovation seminars, these events were organized to encourage business owners to meet and exchange ideas, insights and best practices with the goal of improving the in-store shopping experiences they offered. Generating over 40 reports that provide real-time sales, employee, payment, vendor, inventory and customer data; the insights retailers could gain would help them easily spot trends and make better business decisions.

The type of data analysis the feature yields is comparable to that of wide-scale ERP or business intelligence solutions, but is far more affordable and easier to understand. As of April , Lightspeed was being installed in 1, new stores every month, its software was being used by 23, businesses in more than 30 countries [20] and its transaction volume had increased percent from the previous year. In November , Lightspeed acquired Amsterdam-based eCommerce software developer SEOShop, and announced that it would be expanding its product offering to serve both brick-and-mortar and online retailers.