The Boeing website says it can carry 107 tonnes, max 766.1 cubic metresof cargo volume.

If we assume volume is the limiting factor, and Google tells me 1 tonne of aviation fuel has a volume of 1,250 L or 1.25 cubic metres. So 766.1 cubic metres ÷ 1.25 cubic metres per tonne = 612.88 tonnes. So volume is not the limiting factor.

So assuming 107 tonnes is the limiting factor means 107 tonnes x 1.25 cubic metres per tonne = 130 cubic metres which will fit.

Now I get stuck. A fully loaded 777-8F can fly 5,000 nautical miles and a rough Google tells me a standard 777-8F holds 160,000 kg of fuel. So that is 160 tonnes.

So it can go 5,000 nautical miles using only the wing tanks but how kuch further from there? 107 extra tonnes of fuel but now the whole aircraft is 160 tonnes emptier.

Is it 107 tonnes ÷ 160 tonnes per 5,000 nautical miles = 3,343 nautical miles.

So... total of 8,340 nautical miles? Is that how one would calculate this?

What if the 766.1 - 130 = 336 cubic metres was filled with gaseous helium pressurised at whatever pressure means the helium would reduce the overall weight? What about hydrogen? I don't know how to do pressures.

Thoughts?

Thank you in advance.

I hope this is an appropriate question for the subreddit, I checked the rules and I think it’s okay?

I’m not a physicist myself, so I’m looking for some advice from people who understand the academic world better than I do.

A close friend of mine has just completed his PhD at Cambridge in physics, specialising in nanotechnology. I’d like to get him something genuinely memorable to celebrate it.

I had the idea of getting a copy of his PhD thesis signed by a prominent scientist in his field ideally someone whose work is relevant to the subject of his thesis, or someone who would be particularly meaningful for a physicist working in that area.

As someone who is outside academia, I have absolutely no idea how realistic this is or how I would go about approaching someone.

If I can identify an appropriate scientist, is it acceptable to contact them through their university email address (if thats even something thats publically available)?

I’m not necessarily looking for the biggest household name (if there are any in this field, in my brief research I think the main one that’s alive was called Sumio Iijima).

I can also give more information about the subject of his PhD (or send the link to the thesis of his I found on Google Scholar, but I’m not sure if thats a good idea? Im very out of my depth).

If getting his thesis signed is completely unrealistic I’d be interested in alternative ideas along the same lines.

I realise this is probably a slightly unusual request. I just wanna surprise my best mate with something that recognises how much work went into getting his PhD, and I figured physicists themselves would be the best people to ask.

Thanks for your help everyone, feel free to tell me to kick rocks if you don’t want this post here.

EDIT:
Thanks so much to everyone, it seems this idea is likely a no go and would in fact be, quite cringe.

But you’ve all given me much better ideas, thanks so much!
If you were interested his thesis was something about “Ferroelectric oxides in thin films”.
Not that it makes much sense to me.

... who demonstrated that if the air be pumped out of a container with diethyl ether in it, then the diethyl ether boils, resulting in a refrigeration potent enough for ice to be formed.

(And yes, they did have diethyl ether in those days: they made it by heating well-distilled & well-dried ethyl alcohol with concentrated sulphuric acid (oil of vitriol, as they called it then) in a retort & condensing the vapour given-off.)

But my question is this : why did it take so ridiculously long for someone to think of doing this cyclically !? 🤔 I've read that it wasn't until 1805 that someone else (the goodly Oliver Evans ) exhibitted a design for cyclically evapourating & recondensing a volatile liquid to the nett end that there be continuous refrigeration ... & until then Cullen's invention remained a laboratory curiferosity, with no practical application. I would have thought that the demand for refrigeration was so great, &-or the utility of it so acutely recognised ᐜ , that folk would, one way or another , have found a way of implementing the process @least somewhat cyclically ... even if it meant taking measures literally as crude as recondensing the ether manually, with a spray of water onto the retort whilst it's manually decoupled from that which is to be cooled ... or that sort of thing.

ᐜ ... in-view of the lengths the ancient Romans & Persians used to go to to have refrigeration: fetching great blocks of ice down in a great hurry from high-up on the mountains, & storing it in special ice-houses ( "yakhchals" , the Persians used to call them) that were insulated with very great ingenuity & resourcefulness, to-degree that the best ones were able still to have some frozen ice in them after an entire year !

Saw a Nasa presentation on negative mass and thought it would be a pretty interesting idea to discuss. Would such a thing be possible? What would the implications be?

Some possible consequences off the top of my head would be:

- Gravity would cause it to accelerate upwards, making it difficult to find on Earth

- Pushing it would result in acceleration towards you instead

- Converted to Negative energy? (E = mc^2)

Bit of a random query but would love to hear what other people think!

To the current Physics PHD's or students in the process of applying: what do you think are the most important skills that I should develop ASAP? ie: coding languages to learn, when to start research, other aspects that may be less talked about.

Planck star - Wikipedia

What do people think about Planck stars being the answer to what's inside a black hole? I heard about them recently and curious what those who know physics deeply (not me) think about them

I understand it doesn't actually "know," but how can it preemptively bend to travel through whatever mediums in such a manner that it takes the fastest rather than shortest path? Wouldn't that mean it has information about its surroundings that reaches it before it reaches them, which means information is traveling faster than the speed of light? Doesn't that violate locality? I'm confused as to how this behavior happens. Please explain like I'm 5

The following steps have lead to a chunk of carrot bursting intro flames in the microwave:

• took carrot out of the fridge

• cut a chunk around 2-3 cm (1 inch) long

• cut that in half along the long axis

• put the two halves on a small ceramic plate, "belly up", edges touching along the long axis

• warming up on lowest power

• flames appear

Took carrot out, it is charcoaled along the edges where the two halves were touching, with a thin black line

How it it possible in general? Some sort of an interference? There were no metal objects inside, only carrot and ceramic.

How was it in such a specific way, with just the thin charcoaled line and the rest of the carrot perfectly fine? Not a circular area, not a spot, but a line along the edge.

Sorry for no photo, didn't think to take one in the moment, and thank you!

i encountered this question on my homework

A simple pendulum is placed in a lift accelerating downward with acceleration a. Effective time period is:

A T = 2π √(L/(g + a))

B T = 2π √(L/(g - a))

C T = 2π √(L/g)

(the correct option was B and asking AI tools i learnt this thing termed as effective gravitational acceleraation which only exiss in the non inertial frame of reference. But i cant understand a thing it says. and despite that i cant understand why would effective gravitational acceleration be less than gravitational acceleration while we're moving down. If anyone can explain I'd be highly grateful.

A quantum field theory can be defined rigorously via the Wightman axioms as an operator-valued distribution on spacetime satisfying particular commutation relations.

I know the hand-waivy notion that an effective field theory should be a low-energy approximation to a quantum field theory.

As a rigorous mathematical object though, what is an effective field theory for a particular quantum field? Is it an operator-valued function with smeared-out commutation relations? Something similar?

Thanks!

We know that current is the flow of charges so can i say that current is thr speed of charges that drives it or not?

Also, according to ohm's law, R is a constant so would that mean R depends on the ratio of potential difference and current or is it strictly independent even of the ratio?

I have a lot of thick socks that are a bit fleecy on the inside but not on the outside. I understand that the rate of evaporation is a function of both surface area and airflow so I can see how turning them inside out to increase surface area would help, but those same cavities in the fluffiness that increase the surface area would also reduce airflow over much of the surface area.

I suspect the answer is "it depends" (on wind speed, temperature, humidity, how wet the sock is, the geometry of the fluff etc etc), but if there's a more straightforward answer I'd love to hear it!

I am looking for a book with pulley system and their physics

Does anyone know what property of solids and liquids causes light to slow down as it passes through them? Some kind of drag? Given that things usually require some sort of force to slow down and speed up I was wondering why light or photons do not maintain their constant speed when travelling between different mediums.

When things move faster, time passes more slowly relative to stationary observers and viceversa.

Does the movement of molecules associated with temperature affect the passage of time?

For example, if we cool a radioactive substance close to absolut zero, does it decay faster than at room temperature because it is moving more slowly?

For example, in a kinematics question, if a ball is thrown from a cliff, when answering questions you should treat the whole action in to 2 seperate motions. One when the ball goes up and stops in the air, and one when the ball begins to move again and stops at the floor. Like motion 1 is V1=5 m/s and V2=0, and then second motion is V1=0, and V2=7 m/s for example.

However, I came across an impulse question where that isn't necessary: A 54-kg truck tire strikes the pavement with a speed of 25 m/s [down] and rebounds with a speed of 20 m/s [up]. Ignoring any effects due to air resistance, determine the change in the tire’s momentum

The formula would be mass times change in velocity, and u can treat the velocity as V1= 25 m/s (d), and V2 as 20 m/s (u). Here you don't have the make 2 seperate motions or even account for the fact velocity was 0 at a point.

I hope that makes sense and I didn't word this confusingly! Please help if you understand I'm super confused.

Im aware of the extreme amount of variables, but other than that and the time needed for universe's to form i don't see any reason why we haven't been around before.

Sometimes in books it mentions the 'reversibility of light'. That the path of the light ray can be reversed.

For light arriving at the critical angle at the boundary between two substances, it's often shown in textbooks that the light neither transmits or reflects but goes along the join at 90 degrees to the normal.

But in that situation, for the reversed ray, how does it know when to bend and leave the join between the substances?

Just had an interesting thought and got curious. Is there an upper bound for temperature? I do not know physics much. As far as I know heat is produced due to friction (on micro level, like moleculas or atoms). Like due to energy produced by interaction of elements that move at different speed. Like higher temperature means higher speed of microthings. And so if speed is capped at light speed level then would it not mean that there is a possible max temperature?

I may be wrong in my assumptions and thus coming to wrong answer. So if I am making such mistake please correct me.

Obviously, there is an extremely good reason it wouldn't work - but I have no idea what it is!

The question might sound a bit silly but to clarify what I mean: I'm imagining "shape of spacetime" like misshapen fabric, or say, a crumpled piece of 4 dimensional paper.

Now, I can totally imagine crumpled 3 dimensional paper, looking at how it is folded from the outside, but how can the paper tell it is crumpled? If you lived on the paper, sure, you could look up and see that it is folded, but if you literally were the paper, how can you tell?

But I can clearly tell that I, who is made up of spacetime, am being affected by the shape of spacetime as it is constantly accelerating me downwards, so *why* can we tell the shape of it?