The Speed Of Light ??

Yep. Small, but measurable. They gained a few seconds during that time.

In order for GPS to work, it has to be accurate to around a 10 billionth of a second. With that level of precision, the difference in the speed of the clock on board the satellite is measurably slower.

This is the thing that I have the hardest time wrapping my head around. That something mechanical can be physically slowed down by doing laps around Earth very fast. (17,500 MPH). And at that speed they pass over roughly the same place every 90 minutes. They're really not going anywhere.

It's hard enough to buy into it going from one place to another light years away. Yet we know it's true by the physical example you gave. It's not just an egg headed theory any longer.
 
The original poster applies Newtonian physics to questions of relativity. Time dilation and space contraction may not feel correct, but they have been observed. I don’t want to be insulting, but the original poster questions Brian Cox, but has quite obviously never studied this material. This is a horrible thread, as it introduces doubt about established science for no good reason.
 
I guess I need to start driving faster.
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So after I arrived and looked back through a telescope at Earth, I would see it as it was 2 million years ago?
If you could go faster than light, then sure. But I am no physics guru.

I think many things work on paper, and are mathematically correct, but not possible.
 
@billt460 I've seen Professor Cox speak several times. Highly recommended, when he comes to your town. You may be interested in the KIPAC lectures I post from time to time.

If nothing else, it gives one perspective of our place in the Universe.
And how infinitesimally small we and Earth are. Jupiters great red spot is 10 earths across and has wind speeds of 1,300 mph. The fastest tornado on record had a rotational speed of 330 mph.
 
Well say you took a Timex / Rolex, (i.e. a mechanical watch), to 90% of light speed. Then what. What force is going to slow it down?
There is no "force". It won't slow down for you. For you your clock will still run just as it always has. But for a stationary observer it will run slow compared to their clock because the observer is still travelling through time at c. You on the other hand have dedicated a portion of your c to speed (bought at a price), and therefore your clock runs slow compared to someone who is stationary. But of course your speeds are different, and both must be accounted for.

Everybody is traveling at c and it just depends on how it is being allocated, whether it is through time or through space. @PandaBear probably won't like that analogy and can explain it better.
 
Well say you took a Timex / Rolex, (i.e. a mechanical watch), to 90% of light speed. Then what. What force is going to slow it down?
Whether it’s the decay of cesium (atomic clock), vibration of quartz (watch) or the catchment of a Rolex, the fact is that time itself is what has slowed.

The outside observer can see this.

The clock, or the observer with the clock, cannot, since they are in the same reference frame where the slowing is manifest.

It all sounds counterintuitive. It all sounds crazy. But the fact is that we can measure the effect, and it had to be accounted for in the GPS constellation in particular, or the accuracy would’ve been way off.

There have been lots of proofs of Einstein’s theory of relativity. Mostly it’s the scientific community that takes notice of these things, like the occultation of Mercury (one of the first Astronomical proofs) but the GPS satellite clocks are something that we all use every day.

They’re relatable.

And they experience time differently than we do because of their speed.
 
And they experience time differently than we do because of their speed.
And it should be pointed out that this isn't just some unobservable difference for everyday things. There are practical considerations for us as well, such as GPS satellites. Although the time dilation for them is small their clocks are extremely accurate.
 
Respectfully disagree. These are honest questions, thoughts and considerations that lead to learning. I, for one, appreciate the thread.

Oh yeah, and doubt is good. Questioning is good. In fact, it's all good. Just my 2 cents...
A good number of posts are pointing out that established science should be subject to questioning and to challenge. I completely agree and should have allowed for that crucial aspect of science in my comment.

But that is not really what is happening here. The original poster challenges Brian Cox and tells us (paraphrasing) that certain aspects of relativity don’t feel right.

Then this same person doubles down in subsequent posts and shows a lack of understanding of the science of relativity. This is not a post where thoughtful questions from an informed individual were raised.

That these are honest questions is not really the point. The questions are not expansions on the knowledge base that many high schoolers and any science student has.

Beyond that, the revolution brought about by Einstein’s theory are a priceless intellectual achievement in the modern era.
 
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