AskPhysics

I just wrote this article and I would like your comment:

The Universe Will Not Die a Heat Death

We assume that the universe is expanding according to the Lambda-CDM model with a fixed Lambda constant.

Imagine a central star, like our sun. Two artificial satellites are orbiting this sun in circular orbits in opposite directions. As the universe expands, the orbits of the satellites are elevated, and the satellites thus gain mechanical energy (the sum of potential and kinetic energy). This energy can be released by causing the satellites to collide or by simply having them graze each other. As a result, some of their kinetic energy is converted into heat, which can be radiated away as thermal radiation, and the satellites descend to lower, more inward orbits. The process can then begin anew.

Im in the process on building something similar with the rack you see in the picture.

What I want to know is if its possible to determine the optimal length of the tube on the frame and on the rack to allow the max load under stress without the rack breaking/bending on a spot that its not mounted on the frame, and what would be the max load?

and if it is, how to calculate it? :)

things that i know:

• number of tubes
• length
• diameter
• thickness
• bending tube angle
• stainless steel type

worth saying that this is more of a learning exercise.

My understanding is that "what happened to the antimatter?" is a bit of an open question. How sure are we that all of the matter we can see is in fact matter, and not antimatter?

Antimatter has the same mass, electromagnetic spectra, falls down, etc. Do we have a way of determining which version of matter distant objects are made of?

I think I need to rephrase the question. I'll post again in a few days.

The replies so far have generally been very polite, given the subject. I was nervous about that. Thanks everyone!

... Hear me out, okay?

Back in 2000 I took my first solo, out of state trip, to meet an online friend. When I got off the bus, she greeted me, and let me know that we had to go stop by her friends house on the way back.

She was Wiccan and needed some Spiritual guidance because the night before she saw a black portal open up in the corner of her room that was giving her really bad vibes.

It wasn't my thing, but I never discounted it. Maybe it was real, and if nothing else it's just how her mind is rationalizing things.

But I guess my question is: Does the Scientific Method rule out the possibility that a "real" portal appeared in her room?

Taking wave function probability into account and the absense of data from the room, is it fair to say that the scientific method doesn't rule out the black portal being real?

Looking for black and white answers if possible, but I'd also love to hear your reasoning~

Is it possible to determine the percentage of the gravitational force at a specified distance using only the geometry of the planet?

Example: The ISS at ~420km altitude "weighs" about 90% of what it would on the Earth's surface.

Is there an equation using only geometrical values that would give you this info?

Sorry if this is a naive question (I am in high school), but why do we always talk about ‘ideal’ stuff in physics? The conditions are not possible in real life so why bother with them, won’t the numerical values not accurately represent real life situations?

Edit: I assume we’d at least have to take intended acceleration and the mass of the spacecraft into account, at least, right?

All blades have the same size, 36cm long, aerodynamically well shaped. But. The first weighs 120g, the second 125g… And the third one 210g… This is a small problem. So what are my options now? Making a new blade would be the last option, but do I have any other options?

Pressire acts on all directions, which means that pressure has a direction to act upon, allbeit plural. A scalar quantity is a force that has no direction to act upon. How is pressure a scalar quantity? Shouldn't it be a vector quantity?

In school, I was taught that the speed of light is constant, in the sense that if you shoot a laser off of a train going 200 km/h, it still just goes at a speed of c=299,792,458 m/s, not at c + 200 km/h.

What confuses me about this, is that we're constantly on a metaphorical train:
The Earth is spinning and going around the sun. The solar system is going around the Milky Way. And the Milky Way is flying through the universe, too.

Let's call the sum of those speeds v_train.

So, presumably if you shoot a laser into the direction that we're traveling, it would arrive at the destination as if it was going at 299,792,458 m/s - v_train.
The light is traveling at a fixed speed of c, but its target moves away at a speed of v_train.

This seems like it would have absolutely wild implications.

Do I misunderstand something? Or is v_train so small compared to c that we generally ignore it?

Electricity is in the form of electrons, which have mass. Everything that has mass is influenced by gravity. Therefore, why doesn't electricity fall down to the ground due to being influenced by gravity?

The reason planets orbit stars is due to gravity. The reason stars glow is due to heat. What's the reason for gravity existing?

What are your plans for this community or is it abandoned?

Also, would a region of space where light spends more time traversing it become more massive than a similar region of space where light doesn't spend that much time all else being equal?

Greetings everyone.

Just migrated from reddit. Love to see birth of the communities I was once subscribed to on reddit.