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Hefan Zhang

A Fun Summer in Stanford

posted August 06, 2015

I’ve been doing this internship in Stanford for the last 8 weeks. The last two blog posts are just some random thoughts on geology and astronomy, finally I’m going to write about this internship itself. At the beginning, I didn’t have a lot of fun though, data collection is never fun for me, especially when I need to get those data from a Russian book. But the research part of this internship is really fun. The process of research can always help people do free thinking, so I appreciate that this internship has given me the chance to do research by ourselves.

I would also like to talk about the wonderful field trips. In the first field trip we collected some fossils and learned about the geological formation of the San Andreas Fault. On the camping field trip we went into the San Andreas Fault and collected more fossil. I have to say that it is hard to find the crab fossils. The hiking is also interesting, I never knew that an ancient volcano can be split up by hundreds of miles. The view on top of the mountain is very good and I enjoyed the fresh air up there. I might come back next year and have more fun at Stanford!

Relationship between the Age of Earth and the Age of Rocks on Earth

posted July 15, 2015

Today when we were doing the Wednesday lunch talk, I heard one of the grad students said: “Calcium dating is not working well because sometimes we got rocks that are older the age of earth.” When I heard that, I was thinking: “What’s the problem with rocks that are older than the earth?” According to my knowledge on astronomy, the Earth is formed by rocks ejected from the newly formed Sun, so the rocks on earth should all have the same age as the sun. The sun is 4.6 billion years old and the earth is 4.54 billion years old, which means that all rocks on earth should be older than earth itself for about 60 million years. One might say that the earth was struck by a planet of Mars’ size after 200 million years after it was formed, so most of rocks are still younger than the earth. But they didn’t realize that the Mars-sized planet is also as old as the sun, so the rocks on it is still older than the earth. I cannot imagine that Earth was created out of nothing and all the rocks just appears magically after it was formed.

Well, I know little about geology or astronomy, this is only my opinion on why rocks on earth should be older than the earth itself. Please correct me if I made any mistake.☺

Comment from Noel:

There are two important points here. First, the age of a rock is determined by the time its constituent minerals crystallized from a molten state. The early Earth was entirely molten, so all rocks that have formed on Earth are younger than the Earth's initial coalescence as a molten planet. This also means that rocks formed from younger volcanism will have an age equal to the time of eruption. For example, the rocks that are being erupted today on Hawaii have a radiometric age of 0, i.e., today. Second, dating rocks using Ca isotopes is a difficult technique because of natural contamination. The students were expressing frustration because they know their rock came from Earth (it wasn't a meteorite) and the field context of where the rock was collected indicates that it should be younger than the maximum age of the Earth itself (in fact the oldest known mineral from Earth is slightly younger than the maximum age of the Earth).

A Thought on the History of Life and Methods of Scientific Researches

posted July 04, 2015

“We should consider history as a mirror to the future.” -- traditional Chinese saying. Yes, history can be a reflection of the future. It is true for both the history of human society and the history of life. In human society, history more or less repeats itself, so it is important to analyze the current situation and compare it with historical events so that we can predict what might happen in the future. As for the evolutionary process of living organisms, we can usually find an evolutionary trend by looking at the history of life, and we can use the trend to predict the future of living things on earth. One example is that the maximum body size of organisms has always been increasing since 3.5 billion years ago, so scientists predict that it would keep increasing in the future. So it is important to study the history of life.

Of course, we need to do scientific researches in order to study the history of life. We have to make the most accurate measurements so that we can get the best data for our research, so we need to gather as much related information as possible. Let’s talk about our current research project -- “why have organisms’ body size changed over time?” In my opinion, we have no way to figure out this problem by only looking at the data about the organisms’ body size; we have to know much more than that. It would be very helpful if we can know about the niche under which the organisms live. For example, when we look at the fossil of an organism, we shouldn’t just look at the fossil itself; we should indeed do chemical analysis of the rock in which the fossil is found and study the fossils of other organisms around it. One might say that accurate measurements is toilsome and unnecessary, but the fact is that we have to be accurate to carry out the correct conclusion, or the whole research would be a failure. So we must be as accurate as possible when doing measurements!

Well, you might not agree with me, but please take my words seriously, because we are studying the history of life -- predicting the future of life!!

And I suppose this is the end of this blog post, have a nice day! :-)