It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Just because the difference is small doesn't mean it's not different. Again I'm going to exaggerate the size of the effect and you can hopefully realize the magnitude doesn't change what's happening, just how quickly it happens. Let's say we are in a high gravity environment, higher than Earth. For every year that goes by here, 10 years go by on the ISS.
Originally posted by DenyObfuscation
Let's shift from a GPS sat to the ISS. A clock calibrated to be accurate on the ground is placed on the ISS. Naturally it will be inaccurate while in orbit. I'm told this is due to a difference in the rate of time. I have to ask what about the astronauts on board? They don't drift into the future or the past.
Just because the difference is small doesn't mean it's not different.
Originally posted by DenyObfuscation
reply to post by kthxbai
Since it isn't time that's changing, what causes the different rates that exist in the measurements.
The effects of gravitational gradients(?) on the physical processes of a timekeeping device.
Can you tell me what it is exactly that you disagree with about and why? Do you even have a clue as to what I've said in this thread?
I just gave an example of redshift in my last post which had nothing to do with expanding space. However the redshift from other galaxies in the Hubble relationship doesn't have this cause.
Originally posted by ImaFungi
reply to post by Arbitrageur
If space wasnt expanding would redshift still occur?
Spectroscopy tells us light from other galaxies is red-shifted. The red-shifted photons do have a lower energy level, who said otherwise? See the reference I posted in response to the OP regarding "tired light".
How do we know the photons we detect have been shifted in energy, and the 'redshifted' levels arent just the photons energy level?
The GPS reference link I posted earlier showed numerous sources of errors in the GPS signal, including ionospheric effects, and tropospheric effects, including humidity, among others. Signal strength is more or less an inverse-square relationship, but that's not exactly the source of the errors.
When we send a radio signal to the ISS from earth, does this signal lose strength interacting with all the molecules in its path?
My exaggerated example above occurs because the photons lose energy and the wavelengths increase as they escape a gravitational field. Relative motion can cause similar things. See the wiki on "Equivalence principle", a key concept in relativity.
Does red-shifting have to do with the receiver of the photon (ISS) is moving relative to the photon, and the photons emitter, so because of the motion of the ISS it kinda "catches the signal on the run" and this causes the redshift?
It was a fun thought experiment and I hope you get something out of it but I did by thinking about it even if you don't. It's not something I think about everyday. I left out the word "affect" in one of my edits and it's too late to edit now so insert that if you see a sentence that needs it.
Originally posted by DenyObfuscation
reply to post by Arbitrageur
Appreciate the effort. Hope it's not wasted on me.
I think that's what the scientists with the optical clocks having only a 1/3 meter height difference were trying to do....show various ways of demonstrating relativistic effects. Relativity may be one of the most tested theories so you can find all kinds of experiments verifying it. Here are some other experiments:
I agree, that's why I thought there should be a way to verify the difference if it exists.
Originally posted by Phage
reply to post by DenyObfuscation
I'm not even sure that velocity itself is a factor in the process.
It has to be. Unless you think the speed of light changes.
Considering the Hafele-Keating experiment in a frame of reference at rest with respect to the center of the earth, a clock aboard the plane moving eastward, in the direction of the Earth's rotation, had a greater velocity (resulting in a relative time loss) than one that remained on the ground, while a clock aboard the plane moving westward, against the Earth's rotation, had a lower velocity than one on the ground.
It seems they did, otherwise there would be no point in flying in opposite directions.
I can't determine an effect of velocity (at least the speed portion) on the results. They didn't test for that.
The only way to go "with" or "against" gravity is to gain or lose altitude. It doesn't have anything to do with horizontal motion. By flying with the rotation of Earth you gain velocity relative to the center of the Earth. That is why orbital spacecraft are launched in that direction.
There is an obvious difference from the difference in velocity (direction portion) which I suspect is due to going "with" or "against" gravity, as if it has something like momentum in the direction of rotation.
It's with or against the Earth's rotation. Let's say at a particular latitude, the Earth's "rotation velocity" is about 900mph. If a 400mph plane flies with the rotation it's really going 1300mph, but if it flies against the rotation it's really going 900mph-400mph = 500mph.
Originally posted by DenyObfuscation
I can't determine an effect of velocity (at least the speed portion) on the results. They didn't test for that. There is an obvious difference from the difference in velocity (direction portion) which I suspect is due to going "with" or "against" gravity, as if it has something like momentum in the direction of rotation.
Originally posted by Arbitrageur
I just gave an example of redshift in my last post which had nothing to do with expanding space. However the redshift from other galaxies in the Hubble relationship doesn't have this cause.
Spectroscopy tells us light from other galaxies is red-shifted. The red-shifted photons do have a lower energy level, who said otherwise?
My exaggerated example above occurs because the photons lose energy and the wavelengths increase as they escape a gravitational field. Relative motion can cause similar things. See the wiki on "Equivalence principle", a key concept in relativity.
Originally posted by Arbitrageur
It's with or against the Earth's rotation. Let's say at a particular latitude, the Earth's "rotation velocity" is about 900mph. If a 400mph plane flies with the rotation it's really going 1300mph, but if it flies against the rotation it's really going 900mph-400mph = 500mph.
Originally posted by DenyObfuscation
I can't determine an effect of velocity (at least the speed portion) on the results. They didn't test for that. There is an obvious difference from the difference in velocity (direction portion) which I suspect is due to going "with" or "against" gravity, as if it has something like momentum in the direction of rotation.
Yes I already said several times "Tired light", which even though Swan doesn't realize it, has a tired light hypothesis. I posted a link explaining why it's been ruled out, but it was definitely considered.
Originally posted by ImaFungi
Ok then is there a way redshift from other galaxies can be explained besides spatial expansion?
How many times do I have to say "spectroscopy"? We know the spectroscopic signatures of the elements (using AAS, AES, etc) so we can tell when they are not where they are supposed to be when analyzing starlight, and the difference is the redshift or blueshift. By the way this can also tell us the composition of the stars. Here are some spectroscopic signatures:No one said otherwise, but where does the concept of shifting come in, and how is it measured?
Spectroscopy tells us light from other galaxies is red-shifted. The red-shifted photons do have a lower energy level, who said otherwise?
The latter because it would happen even if there was no atmosphere.
Ok, I will check it out. Is the 'losing energy as they escape gravity field' due to (only slightly as you said above the photons interaction with all the matter on its way out...but mainly) the photon traveling a different geometry of space time as it gets further from the gravitating body?
Planes can measure speed relative to the ground and the air which are usually different. Just because it doesn't make sense to you, doesn't mean it doesn't make sense. They don't take into account if the ground is moving at 900 miles an hour...they just ignore that since they have no reason to consider it, but the folks at NASA have to consider it when they launch East rather than West to get the extra 900mph or whatever it is, boost.
I dont understand how that makes sense. What is a speedometer on a plane set in reference to?
Originally posted by Arbitrageur
Yes I already said several times "Tired light", which even though Swan doesn't realize it, has a tired light hypothesis. I posted a link explaining why it's been ruled out, but it was definitely considered.
Planes can measure speed relative to the ground and the air which are usually different. Just because it doesn't make sense to you, doesn't mean it doesn't make sense. They don't take into account if the ground is moving at 900 miles an hour...they just ignore that since they have no reason to consider it, but the folks at NASA have to consider it when they launch East rather than West to get the extra 900mph or whatever it is, boost.
There are some ideas, but let's say if we are able to figure out dark energy we'll have a better understanding. We haven't figured it out yet.
Originally posted by ImaFungi
Ok, so because tired light is not true, intergalactic space is expanding? Is there an offered theory as to where the extra space is coming from?
I don't know where you got centrifugal force. That's a fictitious force to a physicist. There are 24 hours in a day, and you can trace the distance around the surface of the Earth at any given latitude. That is the distance that is covered in one day at the given latitude, so divide that total by 24 and you get the velocity per hour. At one of NASA's launch sites it's a little over 900mph. You could observe this motion from the moon.
The boost has to do with gravity and/or centrifugal force? Or are those the same thing regarding a rotating and accelerating body?
Originally posted by ImaFungi
The boost has to do with gravity and/or centrifugal force? Or are those the same thing regarding a rotating and accelerating body?
What is a speedometer on a plane set in reference to?
Originally posted by Arbitrageur
There are some ideas, but let's say if we are able to figure out dark energy we'll have a better understanding. We haven't figured it out yet.
I don't know where you got centrifugal force. That's a fictitious force to a physicist. There are 24 hours in a day, and you can trace the distance around the surface of the Earth at any given latitude. That is the distance that is covered in one day at the given latitude, so divide that total by 24 and you get the velocity per hour. At one of NASA's launch sites it's a little over 900mph. You could observe this motion from the moon
Originally posted by Bedlam
Originally posted by ImaFungi
The boost has to do with gravity and/or centrifugal force? Or are those the same thing regarding a rotating and accelerating body?
Nope, just that the Earth is spinning. If you launch towards the east, you get a starting speed that's the rotational speed of the Earth at that altitude. The closer to the equator you are, the bigger the boost.
That's why you can't put as much mass into polar or retrograde orbits, you're either getting no advantage or you're having to overcome the rotational speed of the Earth, so for retrograde launches, you generally do them closer to the poles if you can.
Yes physicists are sure that empty space is not empty. We can characterize some of the properties of empty space. However, I also think it's safe to say these properties are only partially but not fully understood, like we don't know why some values predicted by quantum field theory are not observed, in addition to dark energy observations. So there are some mysteries to solve. And technically, it's not exactly true that "dark energy is only thought to exist because its thought space is expanding". We thought space was expanding in 1997 before the discovery of dark energy in 1998. The unexpected result in 1998 is that the expansion is accelerating...so that's the "dark energy" effect.
Originally posted by ImaFungi
Originally posted by Arbitrageur
There are some ideas, but let's say if we are able to figure out dark energy we'll have a better understanding. We haven't figured it out yet.
Well dark energy is only thought to exist because its thought space is expanding. Are physicist really sure that galaxies arent moving through a nothingness of space, and that space is actually "something"?
It's not that complicated, it's a 913 mph head start going East at Cape Kennedy. So it can affect payload, fuel requirements, final orbital velocity. The orbiting craft can travel the same velocity in either direction, if you give it enough fuel. But it takes a lot less fuel to go in the direction where you have a 913 mph head start. I don't see why this concept is hard.
K, I still dont know why earths rotation helps an orbiting craft travel faster in one way (traveling with the direction of the earths rotation)
The Earth has angular momentum which results in tangential surface velocity. So it's just the result of momentum, which isn't really a force.
In what manner does the rotation of the earth exhibit a force on the body that is desired to orbit the earth?
Originally posted by ImaFungi
?
In what manner does the rotation of the earth exhibit a force on the body that is desired to orbit the earth?