Depends where in space, and on your definition of a 'straight line'.

If you're in intergalactic space, yeah basically - although it would slowly get broken up by cosmic rays of various sorts.

If you're in LEO, it would end up in a very slightly different orbit to you - although in some ways an orbit is a type of straight line.

It probably wouldn't stay up there for too long, atmospheric drag would pull it down a lot faster than a human or a space station due to its higher surface area vs mass ratio - also it might get melted by sunlight.

In other areas in space, you'll have some blend of those effects (plus other smaller ones like solar wind) depending on local conditions.

If you like or prefer videos, Dr Becky, PBS SpaceTime, Anton Petrov, Scott Manley are excellent starting points.

> I've only done basic high-school science

Same (on paper anyway), but I've read a lot since then because it's interesting ;)

> Would that then mean, from a scientific point of view, there are particles that have always and will always exist and cannot be changed or destroyed

Not at all, E²=m²c⁴+p²c² says there's always the opportunity for the energy contained in matter to unravel and just be energy (eg nuclear fission/fusion, proton decay, etc), or vice versa (eg kugelblitz).

> Is this some sort of chemical reaction?

No, it's dramatically more complex than a chemical reaction, see https://en.wikipedia.org/wiki/White_hole#Big_Bang/Supermassive_White_Hole - "The Einstein–Cartan–Sciama–Kibble theory of gravity extends general relativity by removing a constraint of the symmetry of the affine connection and regarding its antisymmetric part, the torsion tensor, as a dynamical variable.
Torsion naturally accounts for the quantum-mechanical, intrinsic angular momentum (spin) of matter.
According to general relativity, the gravitational collapse of a sufficiently compact mass forms a singular black hole.
In the Einstein–Cartan theory, however, the minimal coupling between torsion and Dirac spinors generates a repulsive spin–spin interaction that is significant in fermionic matter at extremely high densities.
Such an interaction prevents the formation of a gravitational singularity.
Instead, the collapsing matter on the other side of the event horizon reaches an enormous but finite density and rebounds, forming a regular Einstein–Rosen bridge.
The other side of the bridge becomes a new, growing baby universe.
For observers in the baby universe, the parent universe appears as the only white hole.
Accordingly, the observable universe is the Einstein–Rosen interior of a black hole existing as one of possibly many inside a larger universe.
The Big Bang was a nonsingular Big Bounce at which the observable universe had a finite, minimum scale factor."

And that's just a postulate/hypothesis, not something we have any definitive evidence for, or can even test with current technology.

> Secondly do we not know as a species why black holes/ white holes are able to exist.

We know many (but not all) details of how black holes form and how they behave - we predicted them, then found a bunch with our telescopes.

I believe there's some contention about how the Pauli exclusion principle gets squashed when a neutron star gets big enough to transition, but perhaps I'm simply not well-read enough.

We do not know what happens beyond the event horizon, although there are several competing ideas even amongst the highest echelons of cosmological theorists and pure mathematicians.

> Third question, have we ever observed a white hole colliding with a black hole.

We're not convinced that the big bang is a white hole, but if it is, it's the only one we've ever seen - there's no evidence that there are (other) white holes in the universe even though they show up in our math.

White holes - the Big Bang is (arguably) an example of one.

> What if a planet has it's magnetic north pointing towards it's star ?

Like Uranus? It's magnetic north only faces the Sun once per year though, because that's how orbits and rotation works…

> We are used to know that the Earth's north is aligned with the sun's north

It really doesn't :P

> Temperature is a measurement of vibrations in particles essentially.

That's the entry-level understanding of it in matter, but the scientists have come up with new better understandings based on entropy - which is how we end up with negative temperatures that are hotter than any positive temperature, and exist in lasers.

> Mathematically time stops in a singularity. If that is so then, in my incredibly layman-style interpretation, Temperature is physically the same as absolute 0 K.

Nope - particles' momentum is related to temperature, and they keep their momentum if you stop time - they can't move anywhere because no time is passing, but their velocity is still non-zero.

This is quite distinct from particles inhabiting the lowest possible energy state (ie being at absolute zero) where they don't move (or do weird stuff) even though time is passing

I don't think temperature depends on time…

This is the heart of the ongoing firewall debate; basically one set of physics says there should be a maelstrom of particles flying around at insane temperatures at the event horizon, but different physics says you shouldn't notice anything at all when approaching or crossing an event horizon because it's a non-local phenomena.

How can an object cross the event horizon when it's a surface where time basically stops, and movement is distance ÷ time?

Add NSWR and FFR to your reading list - that fission fragment rocket has some impressive paper specs, eg Isp of up to 100,000

It's an interstellar object, and we got pretty excited about 'Oumuamua for that reason alone.

It's also obviously artificial.

Biggest issue is that it will take a bazillion years to get anywhere near another star system, let alone one that might host a technologically advanced alien society.

The inscriptions are carefully designed so that the kind of aliens that could actually capture the Voyager record without it being destroyed should have an extremely high likelihood of being able to decode it given the technological level required to capture it without it being destroyed…

But then they go on to say

>> Could it be installed in a cell phone, an electric bicycle, a cordless drill, a car, a house?

which indicates they're thinking of a physical size, as if the chemistry dictates a fixed size somehow - hence why I pointed out that mobile phones and grid-scale storage can both use the same chemistry, so the question as stated doesn't make much sense

> What is the size of the battery? Could it be installed in a cell phone, an electric bicycle, a cordless drill, a car, a house?

I think you're missing the point of the article, it's describing a specific way to arrange the cell electrodes so that the sodium/sulfur chemistry actually functions - the technology could be used to make any size battery once it's commercialized.

The battery in your mobile phone and the hornsdale power reserve (ie a state/province scale battery) have almost the same chemistry, so asking about the size of a battery made with a particular process as if they had any relation with each other is kinda redundant.

> How far away from manufacture is it?

Heh that's a tough one - there's been so many of these sort of papers that have made big claims then faded into obscurity with nothing ever actually coming of it, and so little information from large scale manufacturers about specifically which papers' techniques they're using that the commercialization pipeline is very opaque.

> Are there any estimates of its cost?

Well sodium and sulfur are much easier to find than lithium, and lithium's cost is skyrocketing while the cost of lithium batteries is falling and they're gonna meet in the middle at some point.

I'm more concerned about the apparently critical role of molybdenum in this paper, since it's rather rarer than lithium - but perhaps someone can work out how to get a similar advantage from more common materials now that they know what to search for?

You're after something like this or wikipedia?

High contrast when they reflect the sun against a pitch-black background, plenty of photons for our eyes to pick up.

There's heaps that you don't see though because they're simply reflecting sunlight in a direction other than towards your eyes.

They can still be a problem for long exposures though, since their rounder parts still reflect a little sunlight in most directions.

I don't think so.

In terms of universal entropy, there's still tons of energy locked away in local maxima all over the place - and life is fantastic at finding ways to pull energy out of local maxima and helping it towards a more global maxima, while going about its business of riding more mundane energy gradients.

For example, there's plenty of nebulas that aren't likely to form stars anytime soon, and I'm sure the universe would love someone to plough a bussard ramjet through - and as long as there's elements other than iron that could be fused for more energy than it takes to bring them together, there's energy gradients out there for life to ride.

Also, there's been a thing floating around just recently that suggests we may actually be somewhat early at becoming complex life

> - Current observations and known physics suggest that the known universe, at some point in the past, existed in a very hot state, at a very dense/small scale (by human standards). What happened (or existed) before this point is completely unknown.

Yep

> - There is no evidence or indication to determine a big 'bang' - in the more literal sense - actually occurred prior to this point. Thats just our extrapolated/romanticised way of explaining how we arrived from the earliest-understood-limits of the above (small+dense universe)... to present day observations of a big-cool-increasingly-expanding universe (either realtime or via obvservational glimpses effectively back into long ago via JamesWebb/Hubble etc). > > - There is no evidence to suggest there was 'nothing' at a point prior to this expansion. Thats just a extrapolated/romanticised way of answering the tantalizing question 'what came before?' in a neat way the human mind can quantify. > > - There is no evidence to suggest anything/everything was actually 'created' in the Big bang. Thats just our extrapolated/romanticised way of imagining how the universe came to be. Our knowledge of current physics and models simply state that the universe was once in a dense, small space... nothing about whether it said material was actually 'created' in some kind of event prior to this snapshot state.

Many widely accepted models indicate that spacetime as a whole (ie time + 3D space + all the energy) started at the big bang, so "before" or "prior" have essentially no meaning in this context.

And yeah, our current models of physics have no meaningful suggestions for how the universe began in such a state, just that it did.

Fundamentally, it's the only white hole we've been able to observe - but how or why 4D spacetime plus energy is streaming from this zero surface is essentially unknowable until and unless we find ways to experimentally probe higher dimensional stuff outside our universe (eg Branes).

Doesn't matter.

Cosmic expansion behaves like new empty space is being injected everywhere all at once, not like some sort of border moving away from a specific point - ie more like bread rising in the oven than a spreading puddle.

Thus, the expansion of space looks pretty much the same from all locations.

Here's Dr Don from Fermilab to tell you about it

If you only use the central force theorem with a single body then yeah, gravitational capture looks impossible because there's nothing to remove energy from the original hyperbolic orbit.

If you consider perturbations from eg n-body stuff or aerobraking however, it becomes quite possible ;)

Also, celestial objects don't have a hard boundary on their hill sphere, the border is very fuzzy and shifts around depending on what other bodies are doing.

> I'm sure our own broadcasts fizzle out into noise before they even reach the Proxima system.

Consider that we've only had a few decades of analog transmissions that are receivable from space, and we've rapidly transitioned to small-range high density terrestrial infrastructure with not just QAM but encryption on top of QAM, in addition to very narrow-beam communications with our local(ish) space vehicles out of necessity to make our range reach our heliopause let alone the nearest stars…

The vastness of space and the speed of light teaches us that distances in time are supremely relevant to the Fermi paradox - if a nearby alien civilisation was merely a century or two behind us (basically nothing in the scale of the universe), they'd never know that they missed our golden years of blasting everything into the sky.

I've been to the Honeysuckle creek radio telescope before, and I asked them if any foreign object ever went through their telescopes' aperture - and (with some reluctance) they told me they'd vaporized a bird once, and even that sort of transmission power would be abysmally difficult to detect at stellar distances even if that sort of transmission had another star perfectly behind the spacecraft they were communicating with at the time.

> If the Milky Way is located in the middle of a void

Nope

The issue is that the Fermi paradox has far too many unbounded variables (due to a sample size of one)

We could barely detect ourselves from the nearest star to the sun, let alone across the Milky way or other nearby galaxies - in fact, the entire history of human civilization is too short to have reached the far side of our Milky way galaxy yet.

If there was an alien civilisation a mere dozen or two light years away with a similar level of technological progression, we wouldn't know - and our own galaxy has a diameter of some 105kLy