cryptist said:If Earth is moving with the speed of 800 km/s in universe, then do we travel at 1/375 of the speed of light according to a hypothetical static point in universe?
No, hypothetically there are reference frames in which he is moving as close to the speed of light as you want, but not at the speed of light. As Einstein said, "the velocity of light in our theory plays the part, physically, of an infinitely great velocity" which means you can never reach it.BenG549 said:... and hypothetically there are reference frame in which he is moving at the speed of light.
ghwellsjr said:No, hypothetically there are reference frames in which he is moving as close to the speed of light as you want, but not at the speed of light. As Einstein said, "the velocity of light in our theory plays the part, physically, of an infinitely great velocity" which means you can never reach it.
ghwellsjr said:No, hypothetically there are reference frames in which he is moving as close to the speed of light as you want, but not at the speed of light. As Einstein said, "the velocity of light in our theory plays the part, physically, of an infinitely great velocity" which means you can never reach it.
BenG549 said:I was assuming that, for example if I were in a ship traveling in one direction at 0.5c, someone traveling in the opposite direction at 0.5 would appear to be traveling at the speed of light, as within my reference frame I am stationary... I take it I've made a basic error in my assumption here? Nothing is actually traveling at light speed.
Ahhh, right. Nice one, good knowledge I'll remember that! So in fact the observed speed would be: v = c/(1+0.25)... i.e. 0.8c. Cool.Nugatory said:Nope, speeds don't add that way. In the situation you describe, where u is the speed of the left moving ship (as observed by an observer in the middle) and v is the speed of the right-moving ship (also as observed by an observer in the middle) the two ships will see each other approaching at a speed that is NOT u+v; it will be [tex]\frac{u+v}{1+\frac{uv}{c^2}}[/tex]
The reason you've never noticed this is because c2 is a very large number, so at any of the speeds that we've ever experienced, the difference between the two formulas is not noticeable. When you're talking about things moving at an appreciable fraction of the speed of light, it starts to matter.
somewhere it says Earth is in total moving with a velocity 800 km/s.
cryptist said:If it was real, I would not write hypothetical. Imagine yourself outside of our space-time. Then, you are a static point. I'm talking about that point..
If Earth is moving with the speed of 800 km/s in universe, then do we travel at 1/375 of the speed of light according to a hypothetical static point in universe?
Actually it says "1 second after, Earth will be 800km far away from this point" So I conclude that Earth is moving with 800km/s, of course as you all said, relative to some reference point.
If Earth is moving with the speed of 800 km/s in universe, then do we travel at 1/375 of the speed of light according to a hypothetical static point in universe?
cryptist said:Actually it says "1 second after, Earth will be 800km far away from this point" So I conclude that Earth is moving with 800km/s, of course as you all said, relative to some reference point.
I suspect you got this number from velocity w.r.t. the CMBR (Cosmic Microwave Background Radiation).
Our local group of galaxies is moving at 600 km/s w.r.t CMBR, so that is the approximate velocity of the Milky Way too. Very 'back of the envelope' calculation - add another 220 km/s as the Sun's velocity around the Milky Way center, and you get something roughly around 800 km/s.
CMBR dipole anisotropy
From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 276±3°, b = 30±3°.[60]
DiracPool said:Interesting, can you provide a link for these figures? Especially the CMBR? Thanks.
The Earth's speed in the universe is due to its orbit around the sun. The Earth orbits the sun at a speed of approximately 107,000 kilometers per hour, or 30 kilometers per second. This speed, combined with the Earth's rotation, adds up to a total velocity of 800 km/s.
The Earth's speed in the universe is relatively fast compared to other planets in our solar system. For example, Mercury, the closest planet to the sun, has an orbital speed of around 170,000 kilometers per hour, while Neptune, the farthest planet, has an orbital speed of about 19,500 kilometers per hour.
Yes, the Earth's speed in the universe is not constant. It varies based on its position in its orbit around the sun. When the Earth is closest to the sun, it travels faster, and when it is farthest from the sun, it travels slower. This is due to the gravitational pull of the sun on the Earth.
The Earth's speed in the universe has a significant impact on our daily lives. It is responsible for the changing of seasons, the length of our days, and the strength of our tides. It also affects the Earth's climate and is an essential factor in determining the habitability of our planet.
Yes, the Earth's speed in the universe can change over time. The Earth's orbit is not a perfect circle, and therefore, its distance from the sun and its speed can vary. Additionally, other factors such as gravitational interactions with other planets can also affect the Earth's speed in the universe.