## 1 Introduction  
As virtual reality (VR) technology continues to develop, studies on verifying the effectiveness of learning and training using it have been steadily conducted in various fields. In particular, since the early days of VR research, studies have been continuously conducted to verify the effectiveness of applying immersive VR to science classes because it is possible to experience learning content that is not easy to actually practice and experience through VR. In the initial stage of the field's development, [PERSON] and [PERSON] (1993) performed an experimental study that explored the education applications of VR at Summer Studies in Virtual Reality so as to assess the potentiality of VR as a tool for learning. The experiment was conducted, in which participants created seven virtual reality spaces and made an expedition into them through seven sessions over seven weeks. The seven VR spaces are the Planestcapes of a futuristic world, Virtual Valley, Cloud Lands, Moon Colony made from the imagination of future Moon, Neighborhood, and Medieval Space Station where participants can experience the past and the future together. Mr. Mountain is a personalized world. The result was that a creative teaching-learning environment was created through VR, and the students quickly learned complex concepts and techniques and understood the conception of presence in VR [1]. In a recent study, [PERSON] and [PERSON] (2018) compared the results learned through Head-mounted display (HMD) and desktop slideshow in a science class for college students regarding how cells in the human bloodstream work. Although the learning effect of the use of the desktop slideshow was higher than that of the use of HMD, the learners' interest and motivation were higher in the latter. Based on these results, the possibility of learning using VR was lauded, and it was stressed that while learning using VR does not guarantee improvement in the learning effect at this stage, it showed an improvement of the learners' interest and motivation, which have a critical impact on the learning effect [2]. [PERSON] (2019) used HMD-based immersive VR technologies in elementary school science classes to see if it is possible to have experiential learning similar to real life in a virtual space. He developed lunar exploration content that students could not carry out in real life, and conducted comparative experiments. The result was that the better the VR technology's vividness and interactivity were, the greater the learning effect was, as the learners could have virtual experiences close to the real experiences. Based on the results of such experiment, the findings of such experiment showed that experiential learning with VR is possible and, along with the continuous evolution of technology, experiential learning that offers experience identical to reality in the near future [3]. Furthermore, many researchers conducted studies on the application of VR to science classes, believing that VR-based education provides students with engaging experiences, makes them display more positive attitudes towards a learning topic, and helps them concentrate on the learning content [1; 4; 5; 6]. Aside from science classes, VR is used in various other fields: military education [7; 8], emergency responder training [9], fire safety education [10], construction hazard education [11], psychotherapy [12], phobia treatment and rehabilitation [13; 14; 15], and sports training [16; 17]. Similar to science classes, in most of these other fields, VR is applied to experiences that are hard to reproduce, and in areas where actual training is important. In most of the studies on applying VR in these other fields, it was concluded that education and training using VR could positively impact the learning effect in the long term by improving the learners' interest, motivation, immersion, presence, and flow. There was a study, however, that raised the question of whether an overly realistic VR experience positively or negatively impacts the learning effect [10].