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Gravity by nature is not a force itself, though it can be calculated as such.

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May 14, 2023, 08:19 AM
bobtheelf
Gravity by nature is not a force itself, though it can be calculated as such.
quote:
Originally posted by trapper189:
What would happen if the Sun just disappeared? Would the planets immediately just go flying off into space?


Not immediately. The effects of gravity travel at the speed of light, so it would take about 8 minutes before we noticed we were no longer orbiting. When the big light went out.
May 14, 2023, 08:32 AM
220-9er
Gravity is a force of attraction.
Based on mass.
Tie your hands behind your back and lean forward. Then tell me it's not a force.


___________________________
Avoid buying ChiCom/CCP products whenever possible.
May 14, 2023, 08:38 AM
signewt
quote:
gravity is a force of attraction.

The old argument of 'things always fall DOWN, never fall UP' is a common observation, especially in the Rocket Industry. Otherwise fuel tanks could be far smaller. Also the very sound of that fuel burning is a marker of the very passage of time, as in the reality of 'falling back to Earth' will occur if escaping the overt attraction of Earth gravity doesn't happen before the sound of the fuel burning stops.

I've lost track of what Musk is up to lately, but have not heard of silent electric rockets as of yet.
May 14, 2023, 04:08 PM
Skins2881
quote:
Originally posted by wrightd:
quote:
Originally posted by Rey HRH:
quote:
Originally posted by Skins2881:
quote:
Originally posted by Rey HRH:


While I agree that mass affects time such as the even horizon of a black hole where time stops, I believe the time rate difference in satellites and planes is caused more by speed rather than mass.

As an object's speed increases, time slows down and as the same object's speed increases, it's mass increases as well.


You've got that wrong. Satellites and planes time dilation is due to gravity. Time dilation due to speed is less noticeable until you get significant fractions of the speed of light. It's almost a flat line until you get to 50% then from 90 to 100% the chart turns near vertical.


Okay, I stand corrected. I'm slow because I'm been mostly laying on my back rather than standing up. I don't mind learning something new. I did fact check you using ChatGPT. I use it for a lot of research. I know it does often come up with factually incorrect answers that are sometimes contradictory with an immediately preceding answer it gives.

quote:
What affects the time rate difference of planes and satellites more compared to time on the surface of the earth - is it the relative speed or the mass of the earth? Give references and citations.


quote:
Both the relative speed and the mass of the Earth have an impact on the time rate difference experienced by planes and satellites compared to time on the surface of the Earth. However, the dominant factor in this context is the gravitational potential, which is directly related to the mass of the Earth.

According to the theory of general relativity, clocks in regions with stronger gravitational fields run slower compared to clocks in regions with weaker gravitational fields. This effect is known as gravitational time dilation. The closer an object is to a massive body, such as the Earth, the stronger the gravitational field and the slower time passes.

The time dilation due to gravitational potential is more significant for planes and satellites compared to the time dilation due to relative speed (special relativity) because the speeds of planes and satellites are relatively low compared to the speed of light. The gravitational time dilation effect dominates in this scenario.

References:

Rindler, W. (2006). Relativity: Special, General, and Cosmological. Oxford University Press. ISBN: 978-0198567325.

Hartle, J. B. (2003). Gravity: An Introduction to Einstein's General Relativity. Pearson Education. ISBN: 978-0805386622.

Misner, C. W., Thorne, K. S., & Wheeler, J. A. (2017). Gravitation. Princeton University Press. ISBN: 978-0691177793.

These references provide detailed explanations of the concepts of special relativity and general relativity, including the effects of relative speed and gravitational potential on time dilation. They support the understanding that the dominant factor affecting the time rate difference of planes and satellites compared to time on the surface of the Earth is the gravitational potential, which is determined by the mass of the Earth.

There is a cool youtube video of a professor taking his students to a high elevation with one atomic clock after syncing a second clock at their starting point. When they returned the clock they took with them after driving to the top of a mountain had a different time. That was amazing. Another video is one I think they did in the 70s, syncing two clocks, then flying one of them around the world on a passenger jet, then showing the difference when they returned. Again pretty powerful demonstration of the physics. In both cases, however, no matter how dramtic the difference, you would never be able to notice it yourself, since in both cases this affect is only noticeable from a relatavistic point of view between two different inertial frames of reference (I hope I got that right). Within your own intertial frame of reference (whether going slow or fast etc) everthying is normal to you no matter your speed or gravitational well. It's at the extremes however that I don't understand - the gravity of a black hole, or the speed of light - and that I THINK is where Einsteins equations on this stuff break down. So maybe that's the answer - which is we still don't really know.


Whenever you get infinite numbers then it just means it's not fully understood. Newtonian physics will get you to the moon or Jupiter, and fully explain celestial mechanics. We understand how things work at a celestial scale pretty well. Relativity explains most things at cosmic scales. When we approach the cosmic speed limit or infinite density (not gravity) we don't have the math to explain things. May never have it, even if we did, how do you test it?



Jesse

Sic Semper Tyrannis
May 14, 2023, 07:27 PM
V-Tail




הרחפת שלי מלאה בצלופחים
May 14, 2023, 07:33 PM
bcereuss
quote:
Originally posted by bobtheelf:
quote:
Originally posted by trapper189:
What would happen if the Sun just disappeared? Would the planets immediately just go flying off into space?


Not immediately. The effects of gravity travel at the speed of light, so it would take about 8 minutes before we noticed we were no longer orbiting. When the big light went out.


I think you’re talking about gravitational waves, not actual gravity.
May 14, 2023, 07:59 PM
Pipe Smoker
quote:
Originally posted by bcereuss:
quote:
Originally posted by bobtheelf:
quote:
Originally posted by trapper189:
What would happen if the Sun just disappeared? Would the planets immediately just go flying off into space?


Not immediately. The effects of gravity travel at the speed of light, so it would take about 8 minutes before we noticed we were no longer orbiting. When the big light went out.


I think you’re talking about gravitational waves, not actual gravity.

So how many angels can dance on the head of a pin?
https://en.m.wikipedia.org/wik...nsequence%2C%20while



Serious about crackers.
May 14, 2023, 08:04 PM
bobtheelf
quote:
Originally posted by bcereuss:
quote:
Originally posted by bobtheelf:
quote:
Originally posted by trapper189:
What would happen if the Sun just disappeared? Would the planets immediately just go flying off into space?


Not immediately. The effects of gravity travel at the speed of light, so it would take about 8 minutes before we noticed we were no longer orbiting. When the big light went out.


I think you’re talking about gravitational waves, not actual gravity.


No, I'm talking about the effects of gravity.

https://www.newscientist.com/a...easurement-revealed/