system
Given the following post, respond as if you're commenting on Reddit:
human
Is there still Gs aka Artificial Gravity after a hard burn with no deceleration in space?

I was watching Ad Astra and their trip to Mars from the Moon was 7 weeks. So when they launched they didn't look like they did a deceleration and drifted the rest of the way to Mars. I was wondering if they will still be feeling the Gs instead of happily floating around in the space craft.
gpt
Acceleration "feels like" gravity. Specifically, staying stationary in a uniform gravity field is locally indistinguishable from being accelerated at a constant rate. We say "locally indistinguishable" because you could look out the window and see how the stars are moving to tell the difference. But in terms of *local* effects the physics comes out the same. So if you drop a tennis ball in an accelerating space-ship, it will fall to the ground. And if you drop a tennis ball on Earth's surface, it will fall to the ground in the same way.

But this is only while you're accelerating! *Speed* is a different thing. There is no universal standard for "stationary". That is, there is no way to tell whether one thing is moving and everything else is stationary, or everything else is stationary and one thing is moving. The physics you feel while moving at a constant speed is *identical* to what you feel when you are stationary - because in a sense, you *are* stationary relative to yourself. So once you turn off the engines and are cruising in a space-ship, you shouldn't feel any effective gravity, and will just float around. It doesn't matter how fast you are going relative to anything else.

Free-fall in a uniform gravity field also feels like weightlessness. Everything is getting pulled the same amount, so if you let go of a tennis ball, then relative to you it will float around right where you left it. This is identical to being stationary and having no acceleration. So even if the rocket is technically feeling the pull of the Sun's gravity, everybody will still feel weightless. This is also why people in the international space station are weightless even though the space station is in orbit within Earth's gravity field.