Modern physicists still look mostly at things we can't see. Either very small things in quantum physics or very big things like galaxies. Puting them together is the main problem of modem physics. The universe of space and time described by Einstein is made up of the noisy fast-moving little sub-atomic particles and other small shings. If you want to know how the universe began - with a tiny size but very big mass, then you need a theory that fits both together. At the moment, the theory suggests that the things we can see - stars and planets etc. make up only 5% of the universe. The rest is 25%“dark matter”and 70%“dark energy". A theory that could explain all that would be a “theory of everything”一the real laws of nature. There are already suggestions of what it might be. Scicntists think that the laws of nature might be rather simple, even though the real world is full of strange and beautifully complicated things. One sugestion is called“string theory", the idea is that inside every particle there is some energy that is like the string of a musical instrument - the way it vibrates makes a different sort of particle. At the moment they say there are cightcen sorts.
回答第（47）空
either very smnall things in quantum physics or very big things like galaxies
