Most of the inside of the Earth is made of really hot melted rock. Can We Travel to the Centre of the Earth? Ships float also because they displace a lot of water. So the force upwards is greater than the weight acting downwards and the ice gets pushed to the surface. Since ice is less dense than water, the weight of a piece of submerged ice would be less than the weight of water it displaces. This says that the force or push upwards on an object equals the weight of displaced water. Given that planets are believed to congeal from gas and dust swirling in the same direction around a new-born sun, this latter discovery is especially hard to explain.Īs yet, nobody knows whether the unusualness of our Solar System has anything to do with the human race having arisen to notice it.The Principle of Archimedes explains why ice floats. There are planets in highly elliptical orbits, similar to those of comets.Īnd there are planets that orbit the wrong way around their stars. There are Jupiter-mass planets that must have migrated inward. There are super-compact planetary systems in which all planets orbit closer to their parent star than Mercury, the innermost planet of the Solar System, does to the Sun.
‘Special’ is improbable while ‘typical’ is probable.īut the discovery of planets around other stars – at last count, more than 3,500 have been confirmed – has created a headache. Scientists hate to invoke anything special about our situation in the Universe. These gas giants orbit close to their star and are common in other systems, but not in our own Solar System. And our best theory – quantum theory – overestimates its energy density by a factor of one followed by 120 zeroes!Īn artist’s conception of a hot Jupiter.
It’s invisible, fills all of space and is accelerating cosmic expansion. Only about 4.9% of the mass-energy of the Universe is atoms: the kind of stuff you, me, the stars and galaxies are made of (and, of that, only half has been spotted with telescopes).Ībout 26.8% of cosmic mass-energy is invisible dark matter, revealed because it tugs with its gravity on the visible stuff.Ĭandidates for what makes up dark matter include hitherto unknown subatomic particles and black holes made in the Big Bang.īut, in addition to dark matter there is dark energy, accounting for 68.3% of the mass-energy of the Universe. There is a discovery so amazing that it has yet to trickle into the consciousness of most working scientists: everything science has been studying these past 350 years is but a minor contaminant of the Universe. The ring superimposed on this Hubble image is a representation of the dark matter thought to be causing the distortions in the galaxy cluster. To get from this smaller size to its present size, the Universe had to go through an initial burst of superfast expansion, known as inflation. In other words, there has been insufficient time for heat to travel between them and the temperature to equalise since the Universe’s birth.Īstronomers fix this by maintaining that early on, the Universe was much smaller than expected, so heat got around easily.
#The most unknown things in science movie
Yet, if we imagine cosmic expansion running backwards, like a movie in reverse, we find that parts of the Universe that are on opposite sides of the sky today were not in contact when the fireball of radiation broke free of matter. The weird thing is that its temperature – 2.725☌ above absolute zero (–270☌), the lowest temperature possible – is essentially the same everywhere. It had nowhere to go, so it is still around us today. The heat of the Big Bang fireball was bottled up in the Universe. It shows tiny temperature fluctuations that correspond to regions of different densities: the seeds that would grow into the stars and galaxies of today. A snapshot of the Cosmic Microwave Background – heat left over from the Big Bang – when the Universe was just 380,000 years old, as seen by the Planck Telescope.
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