Scope bandwidth while traveling at 90% of the speed of light? Can dave answer? - Page 1
Forum section: electronics / testgear

author: mrpackethead
author_rank: Super Contributor
timestamp: February 03, 2019, 06:21:25 am
content: It is known that time slows down when you are traveling fast. IN order for us to be able to get to new worlds, it is probable that we will need to equip our space ships with a good workshop including a scope ( or two ). Maybe even a hacked one, to make the budget go faster..However when time warp starts occurring what would happen to the bandwidth of the scope? Would it remain the same, get narrower, get wider?I asked Siri and Alexa what the answer was but neither of them was smart enough to know....Dave, what is the answer for this.

author: Rerouter
author_rank: Super Contributor
timestamp: February 03, 2019, 06:45:16 am
content: the speed of light is relative, so if your travelling at lets say 99.999% the speed of light in a nice fancy lab, and set up to measure the speed of light on your bench, you would measure the same more or less as a person on earth,

author: DaJMasta
author_rank: Super Contributor
timestamp: February 03, 2019, 06:45:41 am
content: Stays the same, because the relativistic effects are in reference to objects at other velocities. So if you're measuring something that's going the same speed as the scope, it's all the same to you, but if you're measuring something going a different speed, its frequency changes. That means the bandwidth of the scope is always the same, but you could gain effective bandwidth by looking at signals behind the scope (opposite of its direction of the scope's movement), where the slowdown effect could let you see signals going at frequencies outside of your normal bandwidth (though they would be seen on the scope as being inside the bandwidth - it's redshift).Very strange theoretical question though....

author: ebastler
author_rank: Super Contributor
timestamp: February 03, 2019, 08:52:00 am
content: So, how about if you measure a stationary object but your scope is moving at 90% of light speed?(Yes, you would need a long probe cable.)

author: IanB
author_rank: Super Contributor
timestamp: February 03, 2019, 09:19:01 am
content: A fundamental principle of physics, "the principle of relativity", says that if you are inside a closed room (spaceship) traveling at constant velocity, then it is impossible to tell from inside the room what what the room's velocity is. This applies to any velocity, including near to the speed of light. If you cannot see outside the room then you cannot know. When moving at constant velocity the laws of physics remain the same, for any velocity.You are aware of this already, as you are on the surface of a rotating earth, which is moving through the galaxy at some considerable speed, in a galaxy that is moving through the universe also at some considerable speed. If you are indoors with the windows closed you really cannot know or tell how fast you may be moving.

author: Rerouter
author_rank: Super Contributor
timestamp: February 03, 2019, 09:27:24 am
content: easy, your cable attenuation would be too high and you would see no signal :pThe cable makes things a pain, so lets just say you send it as modulated light. (the math really doesn't like when you have medium at a gradient of velocities)OK simplification and head cracking math aside, If the scope was moving away from you when it received your signal, the signals would appear redshifted to the scope and your effective bandwidth would be about 2.3 times higher.And if the scope is moving towards you, the signals it received would appear blue shifted, and decrease the bandwidth to 44% the norm.

author: vtwin@cox.net
author_rank: Regular Contributor
timestamp: February 03, 2019, 10:47:37 am
content: If I am travelling at 185,999 miles per second, and I turn on a flashlight, that means light from the flashlight is actually travelling at 371,999 mi/sec?

author: soldar
author_rank: Super Contributor
timestamp: February 03, 2019, 11:10:47 am
content: Quote from: vtwin@cox.net on February 03, 2019, 10:47:37 amThe light is traveling at the speed of light no matter how you look at it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 03, 2019, 12:44:47 pm
content: we are already travelling at the speed of light or probably even faster. if you take the projected source point of the bing bang (or anything on the opposite side) as the inertial frame of reference. so there is not much wonderfull thing about it.https://medium.com/starts-with-a-bang/how-fast-are-we-moving-through-space-985bf470378dunless you can throw your scope at the speed of light away and somehow not losing it in a way that it can slingshot back to you while making a stationery measurement, but i dont think a 300 Mega meter of cable length is feasible, given you can take a measurement snapshot in 1 second. and as other stated, signal attenuation will be another issue.

author: ebastler
author_rank: Super Contributor
timestamp: February 03, 2019, 12:53:17 pm
content: Quote from: vtwin@cox.net on February 03, 2019, 10:47:37 amYes, that's correct. Relativity theory does not apply when you measure in "miles".

author: David Hess
author_rank: Super Contributor
timestamp: February 03, 2019, 02:57:55 pm
content: Quote from: soldar on February 03, 2019, 11:10:47 amSome oscilloscopes start out faster than light exactly because you are looking at it.https://www.oregonlive.com/silicon-forest/index.ssf/2011/09/a_tektronix_oscilloscope_that.html

author: luma
author_rank: Regular Contributor
timestamp: February 03, 2019, 05:41:57 pm
content: Quote from: mrpackethead on February 03, 2019, 06:21:25 amOnly for an outside observer moving at some different velocity relative to you. For you, at your bench in your speedy spaceship, nothing at all changes. Your frame of reference is no different than anyone else’s, the only difference that arises is when you compare your own frame of reference to another’s. Acceleration also plays a role here which is a whole additional topic.In a manner of looking at things, you (and everything else is the universe) are traveling through space time at the speed of light right now. If you’re made of matter, your vector through time is a lot larger than your vector through space. If you’re a beam of light, your vector through time is zero and 100% of your velocity is moving through space.

author: David Hess
author_rank: Super Contributor
timestamp: February 03, 2019, 06:59:58 pm
content: Quote from: 3roomlab on February 03, 2019, 06:10:19 pm

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 03, 2019, 07:31:41 pm
content: Quote from: Rerouter on February 03, 2019, 06:45:16 amRelativity in a nutshell.